From: Jason Gunthorpe <jgg@nvidia.com>
To: Parav Pandit <parav@nvidia.com>
Cc: Leon Romanovsky <leon@kernel.org>,
Doug Ledford <dledford@redhat.com>,
Jakub Kicinski <kuba@kernel.org>, Jiri Pirko <jiri@mellanox.com>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
Michael Guralnik <michaelgur@mellanox.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Saeed Mahameed <saeedm@nvidia.com>
Subject: Re: [PATCH rdma-rc] RDMA/mlx5: Fix devlink deadlock on net namespace deletion
Date: Mon, 19 Oct 2020 16:01:00 -0300 [thread overview]
Message-ID: <20201019190100.GA6219@nvidia.com> (raw)
In-Reply-To: <BY5PR12MB4322102A3DD0EC976FF317E7DC1E0@BY5PR12MB4322.namprd12.prod.outlook.com>
On Mon, Oct 19, 2020 at 01:23:23PM +0000, Parav Pandit wrote:
> > > - err = register_netdevice_notifier(&dev->port[port_num].roce.nb);
> > > + err = register_netdevice_notifier_net(mlx5_core_net(dev->mdev),
> > > + &dev->port[port_num].roce.nb);
> >
> > This looks racy, what lock needs to be held to keep *mlx5_core_net() stable?
>
> mlx5_core_net() cannot be accessed outside of mlx5 driver's load, unload, reload path.
>
> When this is getting executed, devlink cannot be executing reload.
> This is guarded by devlink_reload_enable/disable calls done by mlx5 core.
A comment that devlink_reload_enable/disable() must be held would be
helpful
> >
> > > if (err) {
> > > dev->port[port_num].roce.nb.notifier_call = NULL;
> > > return err;
> > > @@ -3335,7 +3336,8 @@ static int mlx5_add_netdev_notifier(struct
> > > mlx5_ib_dev *dev, u8 port_num) static void
> > > mlx5_remove_netdev_notifier(struct mlx5_ib_dev *dev, u8 port_num) {
> > > if (dev->port[port_num].roce.nb.notifier_call) {
> > > - unregister_netdevice_notifier(&dev-
> > >port[port_num].roce.nb);
> > > + unregister_netdevice_notifier_net(mlx5_core_net(dev-
> > >mdev),
> > > + &dev-
> > >port[port_num].roce.nb);
> >
> > This seems dangerous too, what if the mlx5_core_net changed before we
> > get here?
>
> When I inspected driver, code, I am not aware of any code flow where
> this can change before reaching here, because registration and
> unregistration is done only in driver load, unload and reload path.
> Reload can happen only after devlink_reload_enable() is done.
But we enable reload right after init_one
> > What are the rules for when devlink_net() changes?
> >
> devlink_net() changes only after unload() callback is completed in driver.
You mean mlx5_devlink_reload_down ?
That seems OK then
Jason
next prev parent reply other threads:[~2020-10-19 19:01 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-19 5:27 [PATCH rdma-rc] RDMA/mlx5: Fix devlink deadlock on net namespace deletion Leon Romanovsky
2020-10-19 13:07 ` Jason Gunthorpe
2020-10-19 13:23 ` Parav Pandit
2020-10-19 19:01 ` Jason Gunthorpe [this message]
2020-10-19 19:26 ` Parav Pandit
2020-10-20 11:41 ` Parav Pandit
2020-10-26 13:38 ` Parav Pandit
2020-10-26 13:47 ` Parav Pandit
2020-10-26 13:43 ` [PATCH rdma-rc RESEND v1] " Parav Pandit
2020-10-26 22:25 ` Jason Gunthorpe
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